Repeater apparatus for carrier systems



Nam 13, 11923,

REPEATER APPARATUS FOR 'LAQIEIHH SYSTEMS Filed July 24. 1919 N V EN TOR. fl 1 fl$mma MTORNEY Patented Nov. 13, 1923.

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HAROLD S. OSBORNE, OF NEW YORK, N. Y'.,

ASSIGNOR TO AMERICAN TELEPHONE AND TELEGRAPH COMPANY, A CORPORATION OF NEW 30:: ii;

nnrnA'rna APPARATUS roa CARRIER sys'rmis i v Application filed July 24, 1919. Serial No. 313,082.

To all whom it may concem- Be it known that I, HAROLD S. OSBORNE, residing at New York, in the county of New j York and State of New York, have invented certain Improvements in Repeater Apparatus for Carrier Systems, of which the following is aspecification.

This invention relates to repeater circuits and more particularly to repeater circuits adapted to the amplification of high frequency carrier currents.

Vhere a carrier system is superposed on an ordinary low frequency transmission line, such as a telephone or telegraph line,

and such a line includes a repeater for amplifying the low frequency signals transmitted thereover, it is necessary to make some special provision for amplifying the carrier frequencies transmitted over the 2 line, since the low frequency repeater is not so designed as to efficiently amplify the higher frequencies used for carrier trans mission. Since it is desirable to superpose the carrier system upon the low frequency system with the least possible change and reorganization of the latter, it is desirable.

that-some arrangement be provided whereby the high frequency oscillations may be amplified without disturbing the low frequency repeater organization.

An important feature of the present invention is the provision of means for amplifying the high frequency carrier oscillations Without disturbing the low frequency repeater. This feature, as well as other aims of the invention, are realized in a specially desi ned repeater adapted to amplify all of t e carrier frequencies transmitted over the low frequency signaling circuit, and in an arrangement of said special repeater whereby it' may be connected in.

series with the low frequency repeater normally associated with the lines. The invention also provides for substantially preventing the carrier oscillations from being transmltted .to the low frequency repeater and for preventing the transmission of low frequency signaling currents to the special high frequency repeater. In this manner the. low frequency channel and the high frequency channels are maintained distinct from each other and the high frequency apparatus in the repeater stations may be imposed upon the ordinary low frequency system without materially affecting the organization or properties thereof.

The invention may now be more fully understood by reference to the following description when read in connection with the accompanying drawing, Figure 1 ofwhich discloses a schematic diagram of .a circuit arrangement embodying the invention, and Figs. 2 to 5, inclusive, of which are circuit diagrams of certain details of the apparatus employed in connection with the invention.

In Fig. 1, ML and ML, designate sections of an ordinary low frequency transmission circuit, such as a telephone circuit, these sections being interconnected by a two-way telephone repeater of well known construction comprising amplifiers AE and AW for amplifying low frequency currents transmitted in opposite directions. The repeater apparatus also includes balanced transformers 10 and 10 of the usual type for interconnecting the input and output circuits of the repeater elements with the line sections, the line ML bein balanced by an artificial line or network BIN and the apparatus to the right of the transformer 10 being balanced by an artificial line or network MN.

In order to exclude frequencies without the telephone range, a low pass filter LF may be inserted in the connection to the main line ML and a similar filter LF may be included in the connection between the repeater and the main line section ML,. Filters LF and LF may be of any desired character but are preferably broad band filters of the general type disclosed in U. S; patents to George A. Campbell, 1,227,113 and 1,227,114 dated May 22, 1917. A filter of this type is illustrated in detail in Fig. 4 and comprises a plurality of sections, each consisting of series inductance and shunt capacity so designed as to freely transmit frequencies which lie within the limits of ordinary signal transmission, while substantially extinguishing frequencies lying above said limit. In the special case herein illustrated, in which the arrangement is applied to telephone transmission, the .filters LF and LF should transmit with negligible attenuation frequencies lying within the range of ordinary telephone transmission, while practically art. no further description thereof is deemed necessary.

()rdinarily, in the absence of carrier apparatus, the connection between main line sections ML and ML, extends through the repeater apparatus comprising amplifiers AE and ATV and over a path 13. \Vhere however. the main lines .IL and ML, are to be used for the transmissionof carrier frequencies, as well as ordinary signal frequencies, it is necessary to provide some means for amplifying the carrier frequencies. Accordingly, a specially designed two-way repeater comprising amplifiers Al), and ATV, is connected in parallel with the path 13 and in series with the low frequency repeater AE.-\W already described. Amplifiers AE, and All', may be of any suitable type. but are preferably of the well known push-pull type in which vacuum tubes are used for securing the dcsired amplification. The circuit details of one of these amplifiers are illustrated in Fig. 5, but as amplifiers of this character are well known. no further description is deemed necessary.

The input and output circuits of the amplifiers AE, and AW, are associated with the main line section ML, and the connection leading to the main line section .\[L through balanced transfm'mers 11 and 11 respectively. Main line ML, is balanced by artificial line or network MN, and the apparatus to the left of the re 'u-atcr is balanced by means of an artificial line or network MN,.

In order to exclude low frequency signaling currents from the carrier repeater above described. high pass filters HF, and HF, are provided in the connections leading to the main line sections ML, and ML. These filters are also of the general type disclosed in the Campbell patents above referred to and each consists, as illustrated in Fig. 3, of a plurality of sections comprising series capacity and shunt inductance. The elements of these filters are so proportioned as to freely transmit a band of frequencies above the upper limiting frequency of ordinary signal transmission. while substantially extinguishing currents below said limit. In the particular case illustrated, which applies to telephone transmission, the filters HF, and HF, would be designed to freely transmit frequencies lying above the upper limits of ordinary telephonic transmission, while substantially extinguishing frequencies lying below said limit. In order to balance thefilters HF, and HF,, balancing net works I-IN, and HN, are provided in the artificial line connections. These balancing networks may simply be filters duplicating the filters HF, and HF,, or they may con sistof networks so designed as to have electrical characteristics simulating those of the filters HF, and HF,.

The arrangement of filter just described provides for the exclusion of low frequency currents from the carrier repeater while permitting carrier frequencies to be. freely transmitted to said repeater. In order to prevent carrier frequencies from being diverted around the carrier repeater through the path 13, a low frequency filter LF, similar in all respects to filters LF and LF already described is included in the path 13. The filters LF and. LF associated with the low frequency repeater comprising amplifiers AE and AW permit the transmission of low frequency currents through said repeater but substantially exclude carrier frequencies therefrom. It. is, therefore. necessary to provide a path independent of the low frequency repeater for transmitting carrier frequencies from the main line ML to the carrier repeater. Accordingly a path 12 is arranged in parallel with the low frequency repeater and a high frequency filter HF is included therein for the purpose of excluding low frequency currents from the path 12, while readily permitting the passage of carrier frequencies. The filter HF is of the same type as the filters HF, and HF, already described.

The operation is as follows: Low frequency signaling currents incoming from the line ML are transmitted througlrthe filter LF, through the transformer 10 to the amplifier AE. After being amplified. the currents are transmitted through the filter LF and over the path 13, through the filter LF, to the main line section ML,. Low frequency currents incoming from the line ML, are transmitted over the path 13. through the filter LF,', through the filter LF'. and by way oftransformer 10' to the amplifier AW. Upon being amplified the] currents pass through the filter LF to the main lin; ML.

High frequency carrier oscillations incoming from the main line ML are excluded from the low frequency repeater by the filter LF and pass over the auxiliary path 12.

through the filter HF and then through the filter HF,, and by way of transformer 11' to amplifier A1 3,. Upon being amplified. the highfrequency currents are transmitted throu h .the filter HF, to the main line section l\ High frequency carrier currents incomin are transmitte through the filter HF and 'throu h the. transformer .11 to the amplifier A After being amplified, the currents are transmitted through filter HF and over the path 12, through the filter IiF to the line section While the invention has been disclosed as ap lied to a telephone transmission circuit, it is equally applicable to other types of signal transmission such as, for instance, ordinary telegraph circuits. Where the low frequency range is quite narrow the low frequency filter may be replaced by any e uivalent means having the desired selectivity, such as tuned circuits or anti-resonantcombinations. Similarly, if but one carrier channel is superposed on the low frequency transmission line, the high frequency 'filters may be replaced by some simple form of tunin arrangement.

11 general, while it has been deemed desirable in the interest of clear understanding to illustrate the invention as embodied in a specific form of circuit arrangement, it will be obvious that the general rinciples herein disclosed may be employed in many other organizations widely different from those illustrated without departing from the spirit of the invention as defined 1n the following claims. I

What is claimed. is:

1. In a signaling system, a transmission line adapted to transmit currents of different frequencies, a plurality of amplifying repeaters in said line in series, means to permit only frequencies within one range tobe impressed upon one of said repeaters, and means to permit only frequencies within another range to be impressed upon another of said repeaters;

2. In a signaling system, a transmission line adapted to transmit currents of difiere'nt frequencies, a plurality ofamplifying repeaters in said line in series, an arrangement of filters whereby only frequencies within a certain range will be impressed upon one of said repeaters,- and anot er arrangementof filters whereby only frequencies within another range will be impressed upon another .of said repeaters.

3. In a signaling system, a transmission line adapted to transmit signaling currents and alternating carrier currents upon which signals may be impressed, a plurality of. amplifying repeatersin said line in series, means to permit only signaling currents to be impressed on one of said repeaters, and

-means to permit only alternating. carrier currents to be impressed upon another of said repeaters.

4. In a signaling system, a transmission line adapted to transmit currents of difi'er from the .line section 1H1,

cut frequencies, a plurality of amplifying repeatersin said line in series, an "arrangement of filters to permit only signaling currents to be impressed on one of said repeaters, and another arrangement of filters to permit only alternating carrier'currents to be impressed upon another of said repeaters.

5. In a signaling system, a transmission line adapted to transmit currents of difierent frequencies,. a plurality of amplifying repeaters in said line in series, a parallel path around each repeater,.means associated with one repeater for permitting'only frequencies within one range to be impressed upon said repeater, means in the parallel path about said repeater to permit only.

frequencies within a second range to be:

transmitted thereover, means associated with asecond repeater to permit only frequencies within said second range-to be im-- pressed upon said second repeater, and means 4 in the parallel pathabout said second re-- peater to permit only frequencies within said first range to be transmitted thereover.

6. In a signaling system, a transmission line adapted to transmit currents of different frequencies, a plurality of amplifying repeaters in said line in series, a parallel path around each repeater, a filter associated with one repeater for permitting only fre' quencies within one range to be impressed upon said repeater, a filter in the parallel path about said repeater vto permit only frequencies within -'a second range to be transmitted thereover, a filter associated with a second repeater to permit only frequencies within said second range to be impressed upon said second repeater, and a' filter in the parallel path about said second repeater to permit only frequencies within said first range to be transmitted thereover.

7. In a signaling system, a transmission line adapted to transmit signaling currents and alternating carrier currents upon which signals may be impressed, a plurality of amplifying repeaters in said line in series, I

parallel aths around each repeater, means associated with one of said repeaters for permitting only signaling currents to be im-- pressed upon said repeater, means in the parallel path aboutsaidrepeater to permit only alternating carrier currents to be transparallel paths around each repeater, a filter its associated with one of said. repeaters for permitting only signaling currents to be impressed upon said repeater, a filter in the parallel path about said repeater to permit only alternating carrier currents to be transmitted thereover, a filter associated with a second of said repeaters to permit only alternating carrier currents to be impressed upon said second repeater, and a filter in the parallel path about said second repeater to permit only signaling frequencies to be.

transmitted thereover.

9. In a signaling system, a transmission saeaaeea line adapted to transmit currents of different frequencies, a plurality of amplifying repeaters in said line in series, and means so arranged that one of said repeaters operates to amplify primarily frequencies within one range, and the other repeater operates to amplify primarily frequencies within another range.

In testimony whereof, I have signed my name to this specification this 22nd day of July, 1919.

HAROLD S. OSBORNE. 

